Springboks coach Peter de Villiers has made two changes to his side ahead of Saturday's Tri-Nations clash with Australia in Perth.

South Africa are currently leading the race for the southern hemisphere crown after two victories over New Zealand and another over the Wallabies and victory over the hosts at the Subiaco Oval will see them close in on what would be their third Tri-Nations title.

Ruan Pienaar will start at fullback ahead of Frans Steyn in the only change to the starting side that accounted for the Wallabies in Cape Town on August 8 with Steyn dropping to the bench. In a second change, flank Schalk Burger returns to the bench in place of Danie Rossouw, who is recovering from injury.

De Villiers explained his decision to tweak his side by saying it was important for the team dynamic that Pienaar be given an opportunity to start.

"Both Ruan and Frans are very talented young players," said De Villiers. "Whilst Frans has not let us down it is important to make sure that Ruan is kept motivated and interested. For that reason we have decided to give him a start at the weekend."

When asked whether Pienaar might at times slot into the fly-half position during the game, De Villiers said, "Ruan has been selected to play at fullback and that is where he will concentrate his energies. However, if the situation dictates, as it might, we have an option to make use of him at 10."

Commenting on the return of Burger to the Bok fold, Springbok captain John Smit said the fact that a player of Burger's calibre was starting on the bench was indicative of the progress the team has made.

"Heinrich Brüssow has done well in that position but it is great to have a player like Schalk - with 50 caps - amongst a very capable bench," Smit said.

De Villiers is refusing to get carried away with his side's impressive run of form that also brought them a series victory over the British & Irish Lions.

"We are taking things one game at a time," said De Villiers. "We are going to throw everything into this weekend's match and only then focus on the next game, whatever the outcome. The Wallabies have had a few injury problems but we will not underestimate them in any way. They are playing at home, which is a great advantage and they remain a very good side."

The match will also see scrum-half Fourie du Preez become the fourth Springboks player this season to reach the 50 cap milestone.

"It is a fantastic honour for me to represent the Springboks and it is special to wear the jersey for a 50th time," Du Preez said. "Whilst the milestone has its relevance it is more important that the team does well in its bid to become Tri-Nations champions."